In recent years, major efforts have been made to develop organic semiconducting (OSC) materials in order to be able to produce more versatile, lower cost electronic devices. Such materials find application in a wide range of devices or apparatus, such as for example organic field effect transistors (OFETs), organic light emitting diodes (OLEDs), photodetectors, organic photovoltaic (OPV) cells, sensors, memory elements and logic circuits to name a few only. The organic semiconducting materials are generally present in the electronic device in the form of a thin layer of, for example, between 50 and 300 nm thickness.
Polycyclic aromatic compounds, either as “small molecules”, such as for example pentacene, or in form of polymers, such as for example poly(hexylthiophene), are widely used in organic electronics because of their good semiconducting properties, However, these materials have a number of disadvantages, which hinder large-scale commercial production. In general these polycyclic aromatic compounds are characterized by low solubility and in consequence can often be processed by vapor deposition methods only. Furthermore they are also difficult to synthesize and in some cases, such as for example pentacene, extremely sensitive to oxidation. On top of this, their charge-carrier mobility and on/off ratio still leave room for improvement.
A promising class of conjugated polymers is based on the indenofluorene unit and was first reported in S. Setayesh et al., Macromolecules 2000, 33, 2016-2020 (DOI: 10.1021/ma9914366) as a candidate material for blue light emission in electroluminescent applications. Indenofluorene copolymers have also been disclosed in WO 2007/131582 for application as organic semiconducting material in transistor devices.
Polymers comprising indacenodithiophene units have been disclosed for example in WO 2012/174561; in WO 2012/088698; in EP 2 075 274 A1; in W. Wen et al., Chem. Commun., 2013, 49, 7192 (DOI: 10.1039/c3cc43229g); in C. Y. Yu et al., Chem. Mater. 2009, 21, 3262-3269 (DOI: 10.1021/cm9007798); in C. P. Chen et al., J. Am. Chem. Soc. 2008, 130, 12828-12833; in Y. Sun et al., J. Mater. Chem., 2011, 21, 13247 (DOI: 10.1039/cljm11564b); in J. H. Tsai et al., Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 2351-2360 (2010) (DOI: 10.1002/pola.24002); in Y. Zhang et al., Macromolecules 2011, 44, 4752-4758 (DOI: 10.1021/ma2008699); in S. H. Chan et al., Macromolecules 2008, 41, 5519-5526 (DOI: 10.1021/ma800494k); in I. McCulloch et al., Nature Materials, vol. 5, April 2006, pages 328-333 (DOI: 10.1038/nmat1612); and in Y. C. Chen et al., J. Sol. Energy Eng. 132(2), 021103 (May 3, 2010) (DOI: 10.1115/1.4001150).
However, the reported charge-carrier mobilities reach at best 0.2 cm2/Vs while most of the reported values are well below 0.1 cm2/Vs.
It is therefore an objective of the present invention to provide new organic semiconducting materials for use in electronic devices. Preferably, such new organic semiconducting materials are characterized by advantageous properties in one or more of good processability, high charge-carrier mobility, high on/off ratio, good oxidative stability and long lifetime in electronic devices. Additionally, it is an objective of the present invention to extend the pool of semiconducting materials available to the expert. Other objectives of the present application are immediately evident to the expert from the following detailed description and examples